Year: 2026
Type: article
Abstract: Background and Aims: A compact dielectric wall accelerator (DWA) could lower the cost, thus increasing the accessibility of proton therapy.The DWA uses a virtual traveling wave, created by switching electric fields along a dielectric beam pipe, to accelerate protons.A proof of concept DWA (keV-energy protons) is being developed.This work investigates the construction of the beam pipe, which should maintain 10 -7 Pa vacuum and withstand electric fields of 10 keV/mm.Methods: A modular Rexolite beam pipe was designed, consisting of a 20 mm diameter tube and 2 ASA/ANSI flange connections, interconnected with Torr Seal epoxy.This design allows connection with a proton source and a spectrometer magnet, and, along the beam axis, with radially symmetric waveguides.The beam pipe thickness was optimized by a linear buckling study in COMSOL multiphysics 6.3 to prevent collapse under vacuum (10 -7 Pa), keeping the inner diameter > beam diameter (5 mm).The wall thickness was varied between 0.5 and 5 mm and the maximal von Mises stress and displacement were recorded.Using the optimal thickness, surface flashover was investigated using the electric field at the beam pipe-vacuum interface, for trapezoid voltage pulses with rise and flattop times of 1.2 and 2 ns, respectively, and peak amplitudes up to 25 kV.Results: A 3D drawing of the beam pipe is presented in Figure 1.The von Mises stress and displacement are shown in Figure 2, and are below their respective thresholds of 4•10 6 N/m 2 and 0.5 mm for all wall thicknesses, and converge for a wall thickness ≥ 4 mm.The maximal electric field, given a 1 mm thick waveguide, was 1.23 MV/ m, which is below the 3.6 kV/m surface flashover threshold for a 7 mm Rexolite sample from literature [1].Conclusions: Simulations showed that a Rexolite beam pipe has an optimal wall thickness of 4 mm, and that the electric field during a pulse is lower than the threshold to trigger vacuum surface flashover.Construction of the beam pipe for experimental validation is ongoing.[1] Leckbee, J. J. et al., "Vacuum insulator flashover of ultra high vacuum compatible insulators."2019
Language: English
Subfield: Aerospace Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,700
OpenAlex ID: W7213257580